1. Field of the Invention
The present invention relates, generally, to contractible ladders and, more especially, to such a ladder configured for deployment as an escape ladder proximate an exterior wall of a building from a position interiorly thereof.
2. Description of the Background Art
Safety consciousness is on the rise in the public; and particularly as respects the threat of fire or the like. Fire and/or smoke detectors are becoming commonplace fixtures in many private dwellings and are currently being compelled by local building codes as a requirement for public and/or rental buildings. Many such devices now incorporate emergency lighting to illuminate an escape path in the event of fire. However, in many cases routes through the building structure may be impassible, a problem oftentimes compounded by fear engendered by the emergency. Usually, escape from higher floors in a building by an exterior route is not facilitated, leaving the individuals either trapped within the building or with the ability to escape only by jumping--another perilous situation.
Of course, fire escapes are well known and are routinely associated with so-called "high-rise" buildings. It is far from customary, however, for private homeowners to include these escape provisions. Thus, there have been quite a number of proposals over the years for a collapsible ladder which might conveniently be secured to a building for escape, inter alia, from a fire. In the main, this class of escape ladder is constituted of a fixed rail attached to the building and a movable rail bridged by pivotal rungs whereby the ladder may be maintained in a collapsed configuration but may be deployed to an open, escape configuration should the need arise in the face of an emergency.
U.S. Pat. No. 4,245,717 is generally representative of this variety of escape ladder. It discloses a ladder comprised of two parallel uprights connected to one another by pivotally mounted rungs wherein the ladder is movable from a closed position in which the uprights abut one another to an open position in which the uprights are spaced by the rungs. Support devices are provided for maintaining the ladder in its open position, while a locking device is mounted on the ladder for holding it in its closed position. The latching device itself includes a locking member pivotably connected to the top of one of the uprights and a cooperating member connected to the top of the other. That preference for construction is one principally dictated by concern for unauthorized entry to the building structure via the ladder, since the latch is made accessible only by reaching outside a window near the ladder in order to move it from its closed position to its open position.
U.S. Pat. No. 4,243,119 is also exemplary of this general type of ladder. It too is comprised of a pair of ladder rails joined periodically by pivotal rungs so that it may move from a closed position to an open one for escape purposes. The fixed rail is formed with an ear having an aperture therein for registration with a corresponding aperture formed in the pivotal rail when in the closed configuration. A pin is inserted through the registering apertures for the purpose of maintaining the ladder in the latter form. Again, the latching member is disposed for operation by one attempting to exit the building and would, as with the foregoing, tend to minimize unauthorized use of the ladder by one attempting improperly to gain access to the building from the ground.
Yet another conceptually similar device is disclosed in U.S. Pat. No. 4,037,686. An escape ladder is described there to include a plurality of rungs spanning and pivotally connecting upright rails so that the ladder may be moved from a normally closed to an open, escape configuration. The ladder is maintained in its normal or closed position by a type of pin/registering aperture arrangement much like that discussed immediately above.
U.S. Pat. No. 3,575,263 is another concerned with folding fire escape ladders secured exteriorly of a building. It, like the foregoing, includes rails joined by pivotal rungs. A latch at the uppermost edge of the pivotal rail member is comprised of a flange having a lip for projection over the fixed rail member, which flange is biased downwardly about a pivot point in order to maintain that association. Deployment is achieved by tripping the latch on the opposite side of the pivot point against the biasing force of a spring.
Another type of ladder designed for collapsible storage and extension to an escape position is disclosed in U.S. Pat. No. 3,414,081. The overall ladder construction is generally as aforesaid while the latching member partakes of certain similarities as well. In this case a pivotable latch pin engages a notch on a latch arm provided with a lever extending from the other side of the pivot point. The pin projects outwardly of one of the ladder rails whereas the latching arm is disposed on the other. This device, as with the foregoing, requires deployment by reaching through an open window or the like and tripping the latching mechanism.
U.S. Pat. Nos. 3,025,923 and 278,301 share many of the same features noted above with regard to collapsible escape ladders. Positive latch members are included for securing the two ladder rails in a normal, collapsed configuration and, upon activation of the latching members, the rails separate to a deployed configuration for escape.
U.S. Pat. Nos. 258,186 and 830,678 are remarkable for constructions particularly adapted for multiple story buildings such as, e.g., apartment house structures. A single, collapsible ladder of the variety noted above is set outwardly proximate windows on each floor. A rope member is disposed along the length of the ladder for grasping by an individual at any floor and deployment of the ladder. The '186 patent is further noteworthy insofar as the main rope used for deployment is provided with secondary ropes passing interiorly of the building. Other patents of historical interest include U.S. Pat. Nos. 400,656, 295,127, 274,278, and 248,607. These additional patents add no further insight into an understanding of the construction or use of collapsible escape ladders over that more explicit above.
As is readily apparent from the preceding discussion, all manner and variety of collapsible ladder constructions have been proposed over the last century. However, despite continuing improvements in these devices, many drawbacks remain. For example, the vast majority of escape ladders within this class require deployment from a position exteriorly of the building. Two particular problems of note obtain when the latching mechanisms are associated directly on the ladder requiring manipulation from within the building by reaching through an open window or door. First, these latching members are prone to failure and lack of reliability for their intended purposes due to constant and oftentimes long exposure to the environment. Corrosion can cause failure or, equally probable, the corrosion product may interfere with the proper actuation of the latch. This is compounded by the second problem, the inconvenience of reaching through a window in order to move the ladder into an escape configuration. Understandably, the reasons necessitating escape give rise to a panic response exacerbated (and probably considerably) when confronted with a latching mechanism which has malfunctioned. Thus, there is considerable room for improvement on that approach.
The single patent reference noted above clearly intending deployment from within the building structure (i.e., U.S. Pat. No. 258,186) also admits of the ability to deploy the ladder from an exterior position by one attempting to gain unauthorized access to the building structure. This is an obvious drawback since little has been achieved by trading one source of emergency for another.
Continuing somewhat further along these lines, none of the ladder constructions noted above provides a truly failsafe approach in preventing unauthorized access to the building via the escape ladder. Even those devices specifically structured with an eye toward minimizing the ability for, e.g., a burglar to enter the building are lacking in many respects. For example, merely placing the latch out of reach from the ground does not suffice where it can be manipulated by, e.g., a pole or struck by a projectile and easily released.
Thus, the need exists to provide an improved, collapsible escape ladder which provides the advantages of those suggested in the prior art but which overcomes the drawbacks presented thereby.